This invention relates to a bending device for use in an endoscope or the like.
Generally, an endoscope comprises a hollow body, an insertion tube extending from the front end of the body, a bending tube extending from the front end of the insertion tube, an operating mechanism mounted on the body so as to bend the bending tube in a remotely controlled manner, and one or more wires for transmitting an operating force of the operating mechanism to the bending tube. The operating mechanism, for example, comprises a manipulation knob mounted outside the body, a pulley mounted within the body, and a shaft extending through the side wall of the body and interconnecting the manipulation knob and the pulley. The wire is passed through the bending tube and the insertion tube, and is fixedly secured at its front end to the front end of the bending tube and also is fixedly secured at its rear end to the pulley of the operating mechanism. When the manipulation knob of the operating mechanism is rotated to pull the wire, the bending tube is bent.
The tension of the wire greatly influences the bending operation. More specifically, if the tension of the wire is weak, a play develops in the operation of the manipulation knob. In this condition, in order to bend the bending tube to a desired angle, the manipulation knob needs to be angularly moved to a large extent. In contrast, if the tension of the wire is strong, a large operating force is required, and also the insertion tube and the bending tube are subjected to meandering or torsion, so that the bending tube can not be bent to a desired angle by the operating mechanism.
Japanese Laid-Open (Kokai) Patent Application No. 144178/77 discloses an endoscope in which spring-loaded moving pieces mounted within a body are pressed against a wire so as to always keep the wire taut under a constant tension. In this endoscope, the moving pieces and a spring must be accommodated within the body, which results in an increased size of the body. Further, when the wire is stretched or becomes longer after a long-term use of the endoscope, the amount of deformation of that portion of the wire on which the moving piece acts is increased, so that the resilient force applied by the spring to the wire is weakened. Still further, the resilient force applied to the wire may be weakened because of deterioration of the spring. In these cases, in order to readjust the tension of the wire, the body must be disassembled for the purpose of exchanging the spring. This is a cumbersome operation.
In an endoscope disclosed in Japanese Patent Publication No. 12132/81, an operating mechanism is movable relative to a body in a longitudinal direction of an insertion tube. More specifically, a rectangular slot extending in the direction of the axis of the insertion tube is formed through the side wall of the body. The operating mechanism includes a pair of plates disposed respectively inside and outside the body. The pair of plates are slidable relative to a pair of opposed edges of the slot so as to adjust the position of the operating mechanism, thereby adjusting the tension of a wire. After this position adjustment is finished, the pair of plates are moved toward each other to clamp the side wall of the body therebetween, thereby preventing the operating mechanism from movement relative to the body. This endoscope is complicated in construction, and it is difficult for this endoscope to have a waterproof construction.
Japanese Patent Publication No. 14184/82 discloses an endoscope similar to that disclosed in Japanese Patent Publication No. 12132/81. An operating mechanism of this endoscope has one slide plate. The slide plate is guided by a guide plate mounted in a slot in a body, and is slidable so as to adjust the position of a operating mechanism in the axial direction of the insertion tube. A pin of the operating mechanism is engaged in one of teeth of the guide plate to thereby prevent the operating mechanism from movement relative to the body in the direction of the axis of the insertion tube. This endoscope also has disadvantages similar to those mentioned above with respect to Japanese Patent Publication No. 12132/81.
Japanese Laid-Open Patent Application No. 130037/88 describes in FIGS. 3 and 7 a connecting member which interconnects a body and an insertion tube. The rear end portion of the insertion tube is secured to the front portion of the connecting member. The rear portion of the connecting member is fixed to the body. Therefore, the position of the connecting member relative to the body and hence the position of the insertion tube relative to the body can not be adjusted.
Japanese Laid-Open Utility Model Application No. 57905/84 describes in FIG. 2 a connecting member which interconnects a body and a flexible tube. This connecting member is fixed at a predetermined position relative to the body. Also, in FIGS. 2 and 7 of this prior application, there is shown a retaining member which retains a rear end of a flexible guide tube through which a wire is passed. This retaining member is not fixed to a connecting member, and is fixed to a frame of the body.